Catalyst for hydrocarbon conversion

ABSTRACT

New catalyst containing a carrier, platinum, iridium, manganese and optionally halogen. This catalyst is useful for reforming and dehydrogenation of hydrocarbons.

This is a division of application Ser. No. 424,200 filed Dec. 13, 1973,now U.S. Pat. No. 3,957,686.

This invention concerns a new catalyst containing (a) a carrier, (b)platinum, (c) iridium and (d) manganese.

The invention further concerns the use of this catalyst in hydrocarbonconversion reactions, such as reforming and dehydrogenation.

Catalysts containing supported platinum are well-known, but, in spite ofthe many improvements brought to these catalysts, for example byincorporating additives such as tungsten, molybdenum, germanium,iridium, rhodium, etc . . . , researches are still connected for findingnew catalysts which on the one hand, would give improved yields, ascompared with the present yields, and, on the other hand, would have alonger life than the known catalysts. Efforts are also devoted toimproving the mechanical properties of these catalysts. These catalystsbeing conventionally used in fixed or moving bed, in the form ofagglomerates, for example balls or extrudates, of appreciable size so asto leave a relatively easy passage to the gaseous reactants, the ageingof these catalysts results in the formation of far smaller grains whichprogressively clog the free space so that the inlet pressure of thereactants must be increased, or even the run stopped.

It was known that moderately good yields could be obtained inhydrocarbon reforming or dehydrogenation by using a catalyst comprisinga porous carrier, for example alumina, together with platinum andiridium; it has now been found that this catalyst could acquire animproved activity by incorporating thereto manganese as a third element.

Now, by using a catalyst comprising a porous carrier together withplatinum, iridium and manganese, the yields may be kept constant overlong periods and the mechanical properties of the catalyst are improved;when associated with platinum, iridium results in a longer life of thecatalyst but also in a loss of selectivity, mainly at the beginning ofits life; it has now been observed that manganese compensates for thisselectivity decrease.

The catalyst according to the invention contains (a) a carrier, (b)platinum, (c) iridium, (d) manganese, preferably in the form ofmanganese oxide, and (e), when necessary, halogen, for example chlorineor fluorine.

The carrier comprises at least one inorganic oxide of an elementselected from groups II, III and IV of the periodic classification.Porous alumina, silica, alumina-silica, magnesia, etc . . . may bementioned by way of examples.

The catalyst according to the invention contains, by weight with respectto the catalyst carrier, from 0.005 to 1 %, particularly from 0.05 to0.8 % of platinum, from 0.005 to 1 %, particularly from 0.01 to 0.09 %of iridium and from 0.005 to 5 %, particularly from 0.05 to 3 % ofmanganese, the latter two percentages being expressed as manganese metaland not oxide.

If so desired, particularly when the carrier is alumina, the catalystmay also contain from 0.1 to 10 % and preferably from 0.2 to 5 % byweight of halogen, for example chlorine or fluorine, with respect to thecatalyst carrier.

The catalyst may be prepared according to conventional methodsconsisting of impregnating the carrier with solutions of compounds ofthe desired metals.

We may use either a common solution of these metals, or separatesolutions for each metal or group of metals. Aqueous solutions orsolutions in hydrochloric acid or in an alcohol are prepared. When aplurality of solutions is used, intermediary drying or roasting stepsmay be carried out. A final roasting usually takes place, for example atabout 500° - 1000° C, preferably in the presence of free oxygen, forexample by air scavenging.

As examples of manganese compounds we may mention the manganesenitrates, chlorides, bromides, fluorides, sulfates and acetates, or anyother manganese salt soluble in water or in hydrochloric acid, forexample manganese chloroplatinate.

Platinum may be used in any known form, for example ashexachloroplatinic acid, ammonium chloroplatinate, platinum sulfide,sulfate or chloride. Iridium may be used in any known form, for exampleas chloride, bromide, sulfate or sulfide or as hexachloroiridic,hexabromoiridic or hexafluoroiridic acid.

Halogen may be supplied as one of the above halides, or as hydrochloricor hydrofluoric acid, ammonium chloride, ammonium fluoride, gaseouschlorine or hydrocarbon halide, for example C Cl₄, CH Cl₃ or CH₃ Cl.

A first method of manufacture consists, for example, of impregnating thecarrier by means of an aqueous solution of manganese nitrate or anothermanganese compound, drying at about 120° C and roasting in air for a fewhours at a temperature of from 500° to 1000° C, preferably about 700° Cand carrying out a second impregnation by means of a solution containingplatinum and iridium, for example a solution of hexachloroplatinic andhexachloroiridic acids.

Another method consists of impregnating the carrier by means of a commonsolution of:

1. platinum (for example as hexachloroplatinic acid)

2. iridium (for example as hexachloroiridic acid)

3. manganese (for example as manganese chloride, bromide, fluoride,sulfate or acetate, or any other manganese salt soluble in water or inhydrochloric acid, for example manganese chloroplatinate), and

4. chlorine or fluorine whenever desired.

A further method consists of supplying the metal elements by carryingout a number of successive impregnations equal to the number of metalelements of the catalyst; for example, we introduce first iridium bymeans of a solution thereof, followed, if desired, with drying androasting steps; then platinum by means of a solution thereof, optionallyfollowed with drying and roasting steps, and finally manganese, thislatter impregnation being followed with a drying and roasting step at atemperature of, for example, from about 500° to about 1000° C.

It should be clearly understood that the above impregnation sequence isnot binding and may be modified.

The porous carriers employed for manufacturing the catalyst according tothe invention are well-known and will not be described in greaterdetail.

The so-obtained catalysts may be used in many known hydrocarbonconversion reactions, in place of the previously used platinumcatalysts, for example in reforming, dehydrogenation, aromatization,dehydrocyclization, isomerization and hydrocracking reactions. Thesereactions are conventionally carried out within the broad temperaturerange of from 300° to 600° C. With particular respect to reforming, thelatter is usually carried out at a temperature in the range of fromabout 450° to 600° C, under a pressure of from about 5 to 20 kg/cm², thehourly reaction rate being from 0.5 to 10 volumes of liquid feed (anaphtha distilling between about 60° and 220° C) per volume of catalyst.With respect to the dehydrogenation of saturated hydrocarbons (of from 3to 40 carbon atoms per molecule), the latter is usually carried out at atemperature of from 300° to 600° C, under a pressure of from 0.1 to 20kg/cm², the hourly reaction rate being from 0.1 to 30 volumes of liquidcharge per volume of catalyst. The molar ratio hydrogen/hydrocarbons atthe reactor inlet is usually 0.1 - 30.

The following examples illustrate the invention but are not intended tolimit the scope thereof.

EXAMPLE 1

Two catalysts A and B are prepared, their specific surface being 230 m²/g, their pore volume 54 cc/g and their chlorine content 1%.

These catalysts have been prepared with an alumina having a specificsurface of 240 m² /g and a pore volume of 59 cc/g.

The catalyst A has been prepared by admixing 100 g of alumina with 100cc of an aqueous solution containing:

-- 1.9 g of concentrated HCl (d = 1.19)

-- 14 g of an aqueous chloroplatinic acid solution of a 2.5 % by weightPt content,

-- 1 g of an aqueous chloroiridic acid solution of a 2 % by weight Ircontent, and

-- 2.3 g of manganese nitrate.

The contact is maintained for 5 hours, then the catalyst is centrifuged,dried at 100° C for 1 hour and roasted at 530° C in dry air (drying withactivated alumina). The catalyst is then reduced in a hydrogen stream(activated alumina) for 2 hours at 450° C. The catalyst contains, withrespect to alumina (the amounts are given by weight):

0.35 % of platinum

0.02 % of iridium

0.50 % of manganese (expressed as manganese metal although present asmanganese oxide)

1.10 % of chlorine.

Catalyst B has been prepared according to the same method, but it doesnot contain manganese. Catalyst B contains 1.10 % of chlorine. Thesecatalysts are tested according to the n-heptane test.

The conditions are selected for having the same conversion rate whenusing the catalysts A and B. The experimental conditions are:

-- pressure : 20 bars

-- ratio H₂ /HC (molar) : 5

-- naphtha weight/catalyst weight/hour : 3

The reactor inlet temperature is 490° C ± 2° C. It is so selected foreach catalyst that they give the same conversion (88 % in the twocases).

Table I summarizes, for catalysts A and B, the molar yield of toluene,the amount of light hydrocarbons produced and the ratio toluene/lighthydrocarbons which defines the selectivity of the catalyst. By lighthydrocarbons, there is meant the C₁ -C₄ cut.

The better the catalyst selectivity, the higher the ratio toluene/lighthydrocarbons.

                  TABLE I                                                         ______________________________________                                        Catalyst           A          B                                               ______________________________________                                        % Pt b.w.          0.35       0.35                                            % Ir b.w.          0.02       0.02                                            % Mn b.w.          0.5        0                                               % lights (molar)   35.2       40.2                                            % toluene (molar)  25         24.3                                            Toluene/light hydrocarbons                                                    (molar ratio)      0.710      0.605                                           ______________________________________                                    

This table shows that manganese substantially improves the catalystselectivity.

EXAMPLE 2

From example 1, it seems that the improved results obtained withcatalyst A, when compared with catalyst B, result from the mere addingof manganese to catalyst A. However, when comparing in table II below(heptane test with the same operating conditions as in example 1) theresults obtained with catalyst A to those obtained with catalysts C andD, these three catalysts having the same total content of metal elementsexcept that catalysts C and D do not contain manganese, it appears thatcatalyst A gives the best results. The conversion is 88 % with eachcatalyst.

Catalysts C and D have been prepared in the same manner as catalyst B.Their metal contents are given in table II and they contain 1.10 % ofchlorine.

                  TABLE II                                                        ______________________________________                                        Catalyst       A         C         D                                          ______________________________________                                        % Pt b.w.      0.35      0.35      0.40                                       % Ir b.w.      0.02      0.07      0.02                                       % Mn b.w.      0.5       0         0                                          % lights (molar)                                                                             35.2      40.2      40.2                                       % toluene (molar)                                                                            25        24.2      24.3                                       toluene/light hydrocarbons                                                                   0.710     0.602     0.605                                      (molar ratio)                                                                 ______________________________________                                    

EXAMPLE 3

This example shows (see table III below) the effect of the iridiumconcentration of the catalyst in a n-heptane test, under the sameoperating conditions as in example 1, for a 88 % conversion. The totalcontent of metals is the same in catalysts A, E and F, as well as themanganese content. Manganese is in the form of manganese oxide incatalyst A as well as in catalysts E and F.

Catalysts E and F, whose metal concentrations are given in table III(the manganese concentration is always expressed as elementalmanganese), have been prepared according to the same method as used formanufacturing catalyst A. They contain 1.10 % of chlorine.

Table III shows that an iridium concentration of 0.08 % is satisfactorybut a concentration of 0.15 % (with respect to the catalyst carrier) istoo high and detrimental to the catalytic activity.

                  TABLE III                                                       ______________________________________                                        Catalyst       A         E         F                                          ______________________________________                                        % Pt b.w.      0.35      0.28      0.25                                       % Ir b.w.      0.02      0.08      0.15                                       % Mn b.w.      0.5       0.5       0.5                                        % lights (molar)                                                                             35.2      35.5      46                                         % toluene (molar)                                                                            25        24.9      24                                         Toluene/light hydrocarbons                                                                   0.710     0.700     0.520                                      (molar ratio)                                                                 ______________________________________                                    

EXAMPLE 4

This example illustrates (see table IV) the effect of the manganeseconcentration of the catalyst, in the same n-heptane test as in theabove examples (conversion : 88 %). Catalysts G to M whose metalcontents with respect to alumina are given in table IV have beenprepared according to a method identical to that used for manufacturingcatalyst A. They all contain 1.10 % of chlorine. The % content ofmanganese is expressed as elemental manganese although manganese ispresent in the form of manganese oxide.

                                      TABLE IV                                    __________________________________________________________________________         Pt  Ir  Mn             Ratio of toluene                                       %   %   %    lights                                                                             Toluene                                                                            to light hydro-                                   Catalyst                                                                           b.w.                                                                              b.w.                                                                              b.w. (mol %)                                                                            (mol %)                                                                            carbons(molar)                                    __________________________________________________________________________    A    0.35                                                                              0.02                                                                              0.5   35.2 25    0.710                                           G    0.35                                                                              0.02                                                                              0.004 40.2 24.3  0.605                                           H    0.35                                                                              0.02                                                                              0.04  36.9 24.4  0.660                                           I    0.35                                                                              0.02                                                                              0.06  36.1 24.6  0.682                                           J    0.35                                                                              0.02                                                                              2.8   35.7 24.7  0.690                                           K    0.35                                                                              0.02                                                                              3.2   37.2 24.4  0.655                                           L    0.35                                                                              0.02                                                                              5     38.7 24.3  0.627                                           M    0.35                                                                              0.02                                                                              6     52   23    0.440                                           __________________________________________________________________________

EXAMPLE 5

C₁₀ - C₁₄ olefins must be produced by dehydrogenation of a normalparaffin cut.

A catalyst N is prepared by impregnating tetragonal alumina balls of a69 m² /g specific surface and a 0.58 cc/g total pore volume (averagepore diameter : 100-500 angstroms). 100 g of these alumina balls areimpregnated with 58 cc of an aqueous solution containing 0.160 g ofplatinum in the form of chloroplatinic acid. The contact is maintainedfor 3 hours at the end of which the alumina balls have completelyabsorbed the solution. The balls are dried in an oven at 100°-110° C for6 hours and then roasted in an air stream for 2 hours at 400° C and 2hours at 500° C. The resulting catalyst contains 0.16 % by weight ofplatinum with respect to the catalyst carrier. It has a specific surfaceof 64 m² /g and a pore volume of 0.52 cc/g. It contains practically nochlorine. Once cooled, the catalyst is charged into the dehydrogenationreactor where it is reduced at 530° C for about 12 hours with a hydrogenfeed rate of 50 liters per hour.

In the same manner, three catalysts O, P and Q have been manufactured;catalyst O contains 0.16 % by weight of platinum and 0.04 % of iridiumwith respect to the catalyst carrier; catalyst P contains 0.16 % ofplatinum and manganese oxide (0.08 % of manganese expressed as metalelement); catalyst Q contains 0.16 % of platinum, 0.04 % of iridium andmanganese oxide (0.08 % of manganese expressed as metal element).Catalysts O, P and Q have been prepared by impregnating 100 g of aluminawith 58 cc of an aqueous solution containing:

Catalyst O : 0.160 g of platinum in the form of chloroplatinic acid and0.04 g of iridium in the form of iridium chloride.

Catalyst P : 0.160 g of platinum in the form of chloroplatinic acid and0.08 g of manganese in the form of manganese acetate.

Catalyst Q : 0.160 g of platinum in the form of chloroplatinic acid,0.04 g of iridium in the form of iridium chloride and 0.08 g ofmanganese in the form of manganese acetate.

The C₁₀ - C₁₄ cut is passed over each of the catalysts N, O, P and Q ata spatial velocity of 2 liquid volumes per volume of catalyst and perhour at a temperature of 460°-470° C, an absolute pressure of 1.5 barand a molar ratio hydrogen/C₁₀ - C₁₄ cut of 10 at the reactor inlet; theliquid and gaseous products issued from the reactor have been analyzedas a function of time, by bromine index determination, chromatography ingaseous phase, mass spectrometry and nuclear magnetic resonance; theresults are summarized in table V.

Table V shows that catalyst N, which contains only platinum, has a poorstability (high decrease of the mono-olefin content in about 100 hours).Stability is improved by adding iridium (catalyst O); iridium additionalso improves the catalyst activity. Catalyst P, which contains platinumand manganese, has a good stability but the activity of this catalyst isrelatively poor. Conversely catalyst Q, which contains both platinum,iridium and manganese is stable, has a fairly good activity after 100hours and is more selective after 100 hours than catalysts N, O and P.

Among the four catalysts N, O, P and Q, it appears that catalyst Q givesafter 100 hours, on the one hand, the best yield of mono-olefins and, onthe other hand, the lowest formation of by-products together with thelowest proportion of unconverted paraffins.

                                      TABLE V                                     __________________________________________________________________________                                          Q                                       Catalyst          O         P         0.16% Pt                                content N         0.16% Pt  0.16% Pt  0.04% Ir                                b.w.    0.16% Pt  0.04% Ir  0.08% Mn  0.08% Mn                                __________________________________________________________________________    Age of the                                                                    catalyst                                                                              4    100  4    100  4    100  4    100                                (hours)                                                                       Composition                                                                   b.w. of the                                                                   liquid prod.                                                                  n-paraf-                                                                              61.4 70.5 57.2 66.8 60.8 67.8 60.4 66.5                               fins                                                                          n-mono- 32   25.3 34.5 28.6 30.5 26.8 34.5 30.1                               olefins                                                                       iso-ole-                                                                      fins+paraf-                                                                           1.1  0.7  1.1  0.8  1.6  1.1  0.9  0.8                                fins                                                                          diolefins                                                                             0.9  0.6  0.9  0.6  1.6  1.1  0.7  0.5                                aromatics                                                                             4.2  2.6  4.2  2.1  5.3  3    3.2  1.9                                % b.w. of the                                                                 charge cracked                                                                to C.sub.1 -C.sub.5                                                                   0.4  0.3  2.1  1.1  0.2  0.2  0.3  0.2                                hydrocarbons                                                                  __________________________________________________________________________

What we claim is:
 1. In a process for reforming hydrocarbons in thepresence of a catalyst at 450°-600° C, the improvement which comprisesemploying as said catalyst a new catalyst consisting essentially ofa.alumina b. metallic platinum c. metallic iridium d. manganese in theform of manganese oxide and e. halogen, the catalyst contents by weightwith respect to the alumina being 0.005-1% of platinum, 0.005-1% ofiridium, 0.005-5% of manganese expressed as manganese metal, and 0.1-10%of halogen in the form of halide.
 2. A process according to claim 1wherein the content of manganese expressed as manganese metal is 0.05-3%by weight with respect to the catalyst carrier.
 3. A process accordingto claim 1, there being 0.2-5% of halogen in the form of halide byweight with respect to the catalyst carrier.
 4. A process according toclaim 1, iridium being present in a concentration by weight of 0.01 to0.09%.
 5. A process according to claim 4, manganese expressed asmanganese metal being present in a concentration by weight of 0.05 to3%.
 6. A process according to claim 5, platinum being present in aconcentration by weight of 0.05 to 0.8%.
 7. A process according to claim6, halogen being present in a concentration by weight of 0.2 to 5%.